INTRAMOLECULAR AND INTERMOLECULAR BONDING IN CRYSTALLINE CLUSTERS OF THE TYPE (CPR)(3)M(3)(CO)(3)[M=CO,RH,IR, CP(R)=C5H5,C(5)ME(5),C(5)H(4)ME]

The relationship between molecular and crystal structures of (Cp(R))(3)M(3)(CO)(3) clusters [M = Co, Rh, Ir; Cp(R) = C5H5, C(5)Me(5), C(5)H(4)Me] has been investigated by a combined use of extended Huckel molecular orbital calculations, empirical atom-atom pairwise packing potential energy calculations, and computer graphics. The indenyl derivative (Ind)(3)Ir-3(mu(2)CO)(3) has also been investigated. The molecules present several isomers of similar energies, and the number of bridging carbonyl groups decreases along the family cobalt, rhodium, iridium, as the metal-metal antibonding character of the orbitals populated in consequence of their formation increases. Hydrogen-bonding networks of the C-H- - -O type involving the carbonyl oxygen atoms have been detected in all of these crystalline complexes. Facial and edge bridging CO's are observed to form preferential interactions with respect to terminal ligands. The intermolecular and intramolecular interactions in each case are discussed and compared in crystal isomers and polymorphs.